This invention relates to catalase compositions useful for destroying hydrogen peroxide, for example, hydrogen peroxide used in disinfecting lenses, such as contact lenses. In particular, the invention relates to catalase compositions and methods useful to effectively destroy hydrogen peroxide and disinfect, and preferably clean, such lenses while reducing eye irritation caused by disinfecting the lenses, and to methods for producing such catalase compositions.
Contact lenses should be periodically disinfected and cleaned by the user to prevent infection or other deleterious effects on ocular health which may be associated with contact lens wear. Currently, there are several different conventional systems and methods which enable the user to clean and disinfect his/her contact lenses between wearing times. These conventional cleaning and disinfection systems can be divided into "hot" and "cold" systems. Hot systems require the use of heat to disinfect the contact lenses, whereas cold systems use chemical disinfectants at ambient temperatures to disinfect the lenses.
Within the realm of cold disinfection systems are hydrogen peroxide disinfection systems. Disinfecting hydrogen peroxide solutions are effective to kill the bacteria and fungi which may contaminate contact lenses. However, residual hydrogen peroxide on a disinfected contact lens may cause irritation, burning or trauma to the eye unless this hydrogen peroxide is destroyed, i.e., decomposed, neutralized, inactivated or chemically reduced. Therefore, destruction of the residual hydrogen peroxide in the liquid medium containing the disinfected contact lens is needed to enable safe and comfortable wear of the disinfected contact lens. Liquid media (not including the hydrogen peroxide contained therein) used to disinfect contact lenses should be substantially isotonic, for example, to the human eye, and preferably ophthalmically acceptable so as to reduce the chances of problems caused by placing the disinfected lenses in the wearer's eyes.
Catalase has been effectively used to promote the destruction of residual hydrogen peroxide contact lens disinfectant. Kay U.S. Pat. No. 4,826,658 discloses disinfecting contact lenses with hydrogen peroxide in the presence of catalase immobilized on the container used to disinfect the lenses. Kay discloses that the catalase is absorbed, adsorbed, or chemically, e.g., covalently, bonded to a support material, such as alumina, bentonite, calcium phosphate gels, carbon, plastics (such as polystyrene, epoxy resins, methacrylates and methacrolates), carboxymethyl cellulose, carboxymethylsephadex, collagen, glass and silica gel, with polystyrene activated by gamma irradiation, U.V. light or corona discharge being preferred. The absorbed or adsorbed catalase is subject to being lost in the disinfecting medium and may contaminate the disinfected lenses. Many of the support materials disclosed by Kay are hydrophobic in nature and may inhibit the hydrogen peroxide-containing liquid aqueous medium from ever effectively contacting the catalase. This can result in incomplete destruction of hydrogen peroxide and irritation of, or even damage to, the eye wearing the disinfected lens. In other instances, the immobilized catalase is immediately exposed to the hydrogen peroxide-containing aqueous liquid medium so that the contact lens may not be effectively disinfected before being placed in the eye. Further, relatively sophisticated and complex processing, for example, as noted above, is often required to covalently bond the catalase to the support materials disclosed in the Kay patent.
There continues to be a need for a system which is relatively easy to produce, and effectively disinfects a contact lens and completely destroys the residual hydrogen peroxide disinfectant without contaminating the lens so that the disinfected lens can be safely and comfortably worn.